1. Field of the Invention
The present invention relates generally to the fields of molecular biology. More particularly, it concerns measurement of biological molecules in situ in a tissue sample. Specifically, the invention provides for creation of a series of microwells in a single tissue or tissue region, thereby permitting analysis of proteins, nucleic acids, lipids, carbohydrates, drugs and other biomolecules in a homogeneous set of reactions.
2. Description of Related Art
With the completion of the Human Genome Project, emphasis is shifting to examining the protein complement of the human organism. This has given rise to the science of proteomics, the study of all the proteins produced by cell type and organism. At the same time, there has been a revival of interest in proteomics in many prokaryotes and lower eukaryotes as well.
The term proteome refers to all the proteins expressed by a genome, and thus proteomics involves the identification of proteins in the body and the determination of their role in physiological and pathophysiological functions. The ˜30,000 genes defined by the Human Genome Project translate into 300,000 to 1 million proteins when alternate splicing and post-translational modifications are considered. While a genome remains unchanged to a large extent, the proteins in any particular cell change dramatically as genes are turned on and off in response to their environment.
As a reflection of the dynamic nature of the proteome, some researchers prefer to use the term “functional proteome” to describe all the proteins produced by a specific cell in a single time frame. Ultimately, it is believed that through proteomics, new disease markers and drug targets can be identified. Proteomics also has much promise in novel drug discovery via the analysis of clinically relevant molecular events. The future of biotechnology and medicine will be impacted greatly by proteomics, but advances are needed to realize the potential benefits.
With the availability of DNA microarray analysis, permitting the expression of thousands of genes to be monitored simultaneously, the importance of the proteome cannot be overstated as it is the proteins within the cell that provide structure, produce energy, and allow communication, movement and reproduction. Basically, proteins provide the structural and functional framework for cellular life.
However, there are several impediments in the study of proteins that are not inherent in the study of nucleic acids. Proteins are more difficult to work with than DNA and RNA. Proteins cannot be amplified like DNA, and are therefore less abundant sequences are more difficult to detect. Some proteins are difficult to analyze due to their poor solubility. And unlike DNA, the protein content of a given cell may vary depending on local conditions, even with a single organism or organ.